The present disclosure relates generally to wellsite operations. In particular, the present disclosure relates to formation evaluation involving testing, measuring, sampling, monitoring and/or analyzing downhole fluids using, for example, optical sensors.
Wellbores are drilled to locate and produce hydrocarbons. A downhole drilling tool with a bit at an end thereof is advanced into the ground to form a wellbore. As the drilling tool is advanced, drilling mud is pumped through the drilling tool and out the drill bit to cool the drilling tool and carry away cuttings. The fluid exits the drill bit and flows back up to the surface for recirculation through the drilling tool. The drilling mud is also used to form a mudcake to line the wellbore.
During or after a drilling operation, various downhole evaluations may be performed to determine characteristics of the wellbore and surrounding formations. In some cases, the drilling tool may be provided with devices to test and/or sample the surrounding formation and/or fluid contained in reservoirs therein. In some cases, the drilling tool may be removed and a downhole wireline tool may be deployed into the wellbore to test and/or sample the formation. These samples or tests may be used, for example, to determine whether valuable hydrocarbons are present. Production equipment may be positioned in the wellbore to draw located hydrocarbons to the surface.
Formation evaluation may involve drawing fluid from the formation into the downhole tool for testing and/or sampling. Various devices, such as probes or packers, may be extended from the downhole tool to establish fluid communication with the formation surrounding the wellbore and to draw fluid into the downhole tool. Downhole tools may be provided with fluid analyzers and/or sensors to measure downhole parameters, such as fluid properties. Examples of downhole tools are provided in U.S. Pat. No. 7,458,252, the entire contents of which are hereby incorporated by reference. The downhole tool may also be provided with sensors, such as optical sensors, for measuring downhole parameters. Examples of sensors are provided in Nos. 2007/0108378 U.S. Pat. Nos. 5,167,149, 5,167,149, 5,201,220, 5,331,156, and 7,687,770, the entire contents of which are hereby incorporated by reference.